Mixer, particularly a concrete mixer



Sept 15, 1964 P. AUGUST ETAI. 3,148,867

MIXER., PARTICULARLY A CONCRETE MIXER l f a INVENTORPf Sept. 15, 1964 P. AUGUST ETAL 3,148,867

' MIXER, PARTICULARLY A CONCRETE MIXER Filed Dec. 5. 1960 5 Sheets-Sheet 2 INVENTORS PQM. a v BY vw www W SYM @WG-#1 Sept. 15, 1964 P. AUGUST ETAL MIXER, PARTICULARLY A CONCRETE MIXER 5 Sheets-Sheet 3 Filed Dec. 5, 1960 1NVENTORS MM W United States Patent O 3,148,367 MIXER, PARTICULARLY A CONCRETE MIXER Pablo August, and Ingeborg Wolfes de August, both f Directorio 130, Bernal, Buenos Aires, Argentina Filed Dec. 5, 1960, Ser. No. 73,849 6 Claims. (Cl. 259-160) The present invention relates to mixers and more particularly to concrete mixers of the type including a tube lift for charging purposes.

Known concrete mixers, particularly insofar as medium and large size machines are concerned, are already provided with a tub lift which in its lower position on the ground lloor is charged with the materials to be mixed and which conveys the mixture components into a mixing drum or trough at certain height. The height at which the mixing drum or trough is arranged, is determined by the size of the receptacles, carts and like means used for transportation of the prepared concrete. In combination with the tower slewing cranes nowadays usually employed on the building sites, for the transportation of the concrete from the mixer to the working place, pails or like receptacles are used which are from 1.20 m. to 1.50 m. high and which require a corresponding discharge level of the mixing drurn or trough of the concrete mixer. Therefore, the relatively heavy mixing drum has to be arranged and mounted on a high and strong machine frame with the result that the mixer of these characteristics is rather expensive and diicult or even impossible to be moved from one place to another.

The usual mixers comprising a mixing drum require mixing times of about 90 seconds per batch which under the most favorable conditions can be reduced to a minimum of 60 seconds. Modern mixing devices, however, require a mixing time of from to 20 seconds per batch only and render the construction of small size machines with high output absolutely practicable if in accordance with the short mixing time the operations of charging and discharging may be executed within like short periods of time.

The present invention aims at providing a mixer capable of coordinating the operations of charging, mixing and discharging with such a result that with a relatively light, simple and cheap batch mixer very high outputs may be obtained.

The main object of the 'invention is to provide a mixer, particularly a concrete mixer with tub lift and tub-charging means, wherein a known rotary mixing device is mounted on a rotary shaft extending longitudinally through the tub of said lift to provide a liftable mixing trough, and wherein inclined guide rails of the tub lift form part of the machine frame of the mixer, comprising a pair of shafts rotatively mounted at the top of said machine frame, a pole changing electric motor carried by said frame and operatively connected with a first shaft of said pair of shafts, a toothed wheel iixedly mounted on said rst shaft and meshing with a second different toothed wheel on the second shaft of said pair of shafts, said second toothed wheel lincluding a free wheel hub, at least one irst rope drum xedly mounted on said rst shaft, at least one second rope drum xedly mounted on said second shaft, and at least one rope having one end fastened on said first rope drum and its other end on said second rope drum and laid in several windings around a helically grooved pulley provided on said rotary shaft of the said mixing device.

The mixer according to the invention, by virtue of the characteristic features set forth, as compared with any known mixers, is not only considerably simplified, but also very economical in its construction, operation and output.

3,148,857 Patented Sept. 15,. 1964 ice Further characteristic and advantageous features of the invention will result from the following description of a preferred embodiment as shown by way of example only on the accompanying drawings whereon:

FIGURE 1 is a schematic side view and FIGURE 2 a schematic front view of the mixer, whereas FIGURE 3 schematically shows the mixer with its charging device according to the invention.

The mixing trough 1 which at the same time constitutes the transport tub of a lift, is provided with carrier wheels or rollers 2 and arranged for its displacement on a pair of guide rails 3. These inclined rails 3 together with cross members 4 and a main frame 5 form a rigid machine frame which may be provided with carrier wheels 6 conveniently so arranged that after tilting the machine frame from its vertical working position as shown to a horizontal position they provide for the possibility of readily moving the mixer from one building site to another.

The mixing trough 1 is semi-cylindrical and is provided with a driving shaft 7 carrying within said trough a known rotary mixing device (not shown). The trough wall adjacent the guide rails 3 is provided with an extension 8 projecting in a direction tangential to the semi-cylindrical trough body. The front walls of the trough 1 are formed with extensions 10 which together with said tangential extension 8 form a `discharge slide or funnel when the mixing trough is in its upper discharging position. In the opening of the mixing trough 1 above its mixing device there is conveniently provided a grating 9 which extends over the whole area of said opening except its portion laterally confined by the front wall extensions 10. For performing the mixing operation, the non-illustrated mixing device is caused to rotate clockwise as viewed in FIG. 1 with the direction of rotation being indicated by the arrow a in the upper position of the mixing trough 1 so that when the mixing trough in its upper position is tilted for discharging the concrete, the mixing device which during this operation continues to rotate in the same direction accelerates this discharge.

On the ends of the shaft 7 extending beyond the front walls of the mixing trough 1 there are provided rope pulleys 11 so constructed that they form several turns of helical guide grooves for the ropes or cables 12 which thus are caused to pass in several windings of like diameter around said pulleys.

For operating the ropes or cables 12, two shafts 13, 14 with rope drums 15, 16 are rotatively mounted at the upper end of the main frame 5. The shaft 13 carrying the drums 15 is provided with a chain wheel or sprocket 17 which by means of a chain is operatively connected with a reversible electric motor 18. The two shafts 13, 14 are operatively interconnected by meshing toothed wheels 19, 20 of which the toothed wheel 20 is arranged in such a manner that it operates the shaft 14 with the rope drums 16 only in the direction indicated by the arrow b, for instance, by means of a non-illustrated free wheel hub as is well known in the art. When the toothed wheel 20 is rotated in the opposite direction, indicated by the arrow c, however, the shaft 14 and the drums 16 are not rotated therewith. Therefore, when the rope drums 15 are operated in clockwise direction to lift the mixing trough 1 from its lower position, the drums 16 uncoil first the rope lengths wound thereon and thereafter hold fast the rope ends so that the drums 15 start lifting the trough 1, whereas when the motor 13 is reversed and the drums 15 are caused to rotate in opposite direction so as to uncoil the ropes 12 therefrom, the drums 16 are also caused to rotate to wind up ropes. Due to the gearing between shafts 13 and 14 a greater length of rope is unwound during this time from each drum 15 than is wound on each drum 16 so that the trough 1 is lowered.

l The electric motor 18 according to the invention is provided With pole changing connections and constructed for voperating with different speed in one and the opposite direction. The pole changing operation advantageously may be effected automatically by means of switches 30, 31 arranged, for instance, near the upper and/ or lower ends of the rails 3 Within reach of a switch-operating means (not shown) provided on the mixing trough 1 and connected to the motor in a well known manner to cause reversal of the direction of rotation and change of speed of the motor during engagement of the switch operating means with the switches 30 and 31, respectively.

In view of that for practical reasons the mixing trough advantageously has a length of 1.00 m. and the pails and carts for transportation of the concrete are relatively smaller in width, below the discharge slide 8, of the mixing trough in its upper discharging position, there is conveniently provided an inclined guide plate 21 with uprght side walls 22. In combination herewith a baille plate 23 is secured to the main frame 5, in such an arrangement that these plates 21, 23 and side walls 22 form an additional discharge funnel capable of being provided with a sliding door'or the like, in which case said funnel is conveniently constructed of such dimensions that it may take up at least one complete charge of the mixing trough with the advantageous result that discharge of the concrete from the mixing trough may be effected in a given case independently of the presence of a transport cart or the like.

In order to fully describe the operation of the mixed according to the invention, it has to point out what fol lows:

If the mixing trough is provided with a modern mixing device and has a diameter of about 60 to 75 cm., a revolving speed of 40 to 45 r.p.m. is required. A diameter of about 60 to 75 cm. is the usual diameter of mixing troughs of a length of 1.00 to 1.50 m. having a capacity of 150 to 200 litres of materials to be mixed. These dimensions are also determined by the fact that for transporting the mixer on a truck its overall breadth should not exceed 2.00 m. and should be less than 1.70 if the mixer mounted on carrier wheels is moved by trackage.

As already mentioned the mixing time of a modern mixing device is about l5 to 20 seconds per charge at a revolving speed of 40 to 45 r.p.m. At a lower number of revolutions of the mixing device the mixing time of to seconds is not sutlicient. The height of lift of the mixing trough from its charging position on the ground until its upper discharging position is of about 1.60 m. In the case of a cavity in the ground being provided for the charging position of the mixing trough the height of lift is increased to about 2.40 m.

For ropes or cables having a diameter of 8 mm. the diameter of the rope drums and pulleys should be at least 140 to 160 mm.

When the rope drums 1S driven by the motor 18 are operated at a speed of 42 r.p.m., the rope velocity is of 36 cm./sec. The ropes 12 pass several times around the rope pulleys 11 of the shaft 7 and their ends are lixed on the rope drums 15 and 16, respectively. In the event the rope ends fixed on the drums 16 would be secured to a ixed point of the machine frame, the mixing trough at a lifting speed of 18 cm./sec. and a height of lift of 1.60 m. would reach its upper discharging position in about 9 seconds. This period of time available for the mixing operation is too short. Even in the case of the mixing trough being lifted out of a cavity provided in the ground and of the so increased height of lift of 2.40 m., the time of about 13 seconds then available for the mixing process is rather short.

This problem is solved by the present invention in such a manner that the ropes 12 as already mentioned are not secured to xed points of the machine frame, but to the rope drums 16. These rope drums 16 as stated are operated by a toothed gearing 19, 20, which may be interchangeable, from the shaft 13 carrying the rope drums 15, and this in such a manner that said rope drums 16 rotate and wind the ropes 12 up only when the drums 1S uncoil said ropes and permit the mixing trough to move down- Wards.

If the ratio of the toothed gearing is e.g. 1:3 with the bigger gear arranged on shaft 14, as shown in FIG. 2, and the electric motor 18 is according to the invention a motor with a pole changer and arranged for making 1400 r.p.m., for the lifting movement, and 2800 rpm. for the lowering movement of the mixing trough, the operation of the mixer is as follows:

The drums 15 and 16 have equal diameters, as shown in FIG. 2, and assuming that these diameters are dimensioned that during turning of the motor at 2800 rpm. the ropes are uncoiled from the drums 15 with a velocity of 72 cm./sec., the resulting lowering speed of the mixing trough will be :24 ern/sec.

When the path of lift is 2.40 m., the lowering movement of the mixing trough from its upper discharging to its lower charging position will take l0 seconds. During these l0 seconds the rope drums 16 will wind up 2.40 m. of the ropes 12. When now for lifting the mixing trough the poles of the motor 18 are changed, the ropes are wound up again on the rope drums 15, however, with a velocity of 36 cm./sec., but before the mixing trough is lifted, the 2.40 m. of ropes have to be rst uncoiled from the rope drums 16 which now by virtue of the free wheel hub provided in the toothed wheel 20 are disconnected from the driving shaft 13 and rotate idly; therefor 6.7 seconds are required and thereafter the mixing trough starts its lifting movement and requires for being lifted to its upper discharging position 13.3 seconds, because the lifting speed is but one half of the rope velocity. Consequently there is a total time of 6.7-]l3.3=20 seconds available for the charging operation and simultaneously for the mixing process, because the mixing device is operated during all this time.

In the event that the mixing trough in its charging position is not lowered into a corresponding cavity in the ground and that for this reason the height of lift is reduced to 1.60 m., by interchanging the toothed opening Y19, 20 the gear ratio is changed to 1:2 and then the 0peration is as follows:

For the lowering movement of the trough the rope drums 15 uncoil the ropes again with a rope velocity of 72 ern/sec., Whereas the drums 16 wind the ropes up with a rope velocity of 36 cm./sec. The lowering speed of the mixing trough consequently is of 36:2:18 cm./sec.; it will reach its lower position within 9 seconds. During these 9 seconds the drums 16 will wind up about 3.20 m. of the ropes 12. After changing the poles of the motor 18, the drums 15 wind the ropes up with a velocity of 36 crn./ sec. and require about 9 seconds for uncoiling the ropes from the drums 16. Thereafter the mixing trough is lifted and with a lifting speed of 18 cm./sec. reaches its upper discharging position within about 9 seconds, so that there are 18-seconds available for the mixing process.

Consequently according to the invention by changing the gear ratio of the interchangeable toothed gearing 19, 20, it is possible to always provide the required mixing time. The mixer further offers the advantage that the beginning of the mixing operation i.e. the start of the mixing device in the mixing trough does not coincide with the beginning of the lifting movement and that by virtue hereof an overload of the motor at its start is avoided. An additional advantage consists in that the material is already being mixed during the charging operation; by virtue hereof, on the one hand, the start of the mixing device is facilitated because there is no material or only a small quantity of material present in the trough when said device is started, and on the other hand, the charging period and the mixing period overlap one another with the result that the elaboration of a batch requires less time.

In order to carry out the charging operation within a few seconds only, it is convenient to have all the materials to be mixed previously proportioned by volume or by weight and available in a suitable receptacle. In the case of small mixers of about 100 to l5() liters, the mixture components inclusive cement are conveniently charged in .so-called Japanese carts and by means of these carts may then be introduced within a few seconds into the mixing trough as soon as it reaches its lower charging position.

For charging bigger mixers, the present invention provides the same with a charging device comprising a pair of rails 24 and a car 25 on said rails operated by means of a winch in a manner similar to that of the known Scrapers. The car 25 is provided with a pair of carrier wheels or rollers 26 arranged substantially below the centre of gravity and with a pair of additional rollers 27 arranged near the rear end of the car for the purpose of assisting the rollers 26 in supporting the car on the rails 24 without preventing the latter from being tilted around the axle of the carrier wheels or rollers 26. At its front end the car comprises a hinged trap-door 28 and in its interior is provided with adjustable and liftable partition walls 29 for proportioning the mixture components by volume. The rails 24 are so arranged that their ends provided with suitable stop members (not shown) are situated laterally above the mixing trough 1 (FIG. 3) in its lower charging position, so that this trough may freely move from its upper to its lower position without touching the car 25 in its position ready for being tilted and discharging its contents into the mixing trough. In its tilted position the car 25 with its front end is, however, situated on the path of the trough so that, when the latter after being charged is lifted, it will strike the car 25 and push the same backwards for being filled again, the rails 24 having such an inclination that the pushed car will automatically return to its filling station.

Instead of the partition walls 29 provided in the car 25 for proportioning the mixture components by volume, the same may also be provided with weighing means for proportioning the materials by weight. Charging of the car 25 is, of course, also possible from one or several silos or deposits in a known manner.

The charging device as hereinbefore described is essential for the proper development of the mixing and discharging operations of the mixer. Usually the materials to be mixed are supplied to the mixing trough by means of a scraper, particularly in the case of big mixers comprising a tub lift. The scraper, however, has a capacity of about 75 litres only and it is therefore necessary to operate therewith several times for filling the tub of the lift or, in the present case, the mixing trough 1. It will be readily understood that by means of a scraper the charging operation cannot be finished within 5 seconds. The scraper is further unable to proportion the materials to be mixed.

As compared herewith the charging device according to the invention not only supplies the materials to the mixing trough, but also permits the proportioning of the materials by volume or weight. The discharge of the materials from the car 25 into the mixing trough 1 does not require more than 5 seconds. With the aid of this charging device the periods of `time employed in the operation of the mixer are as follows:

Height of lift Discharge of the supply cart during the period of Sec. Sec.

uncoiling the ropes from the drums 16 5 9 Lifting movement of the trough 13 9 Lowering movement of the trough 10 9 Time for twice changing the poles of the motor 18-- 2 2 Total time for elaboration per batch 30 29 A mixer for 260 litres of materials to he mixed i.e. about 200 litres of prepared concrete, as constructed according to the invention, has a weight of about 650 kg. and requires an engine of 7.5 HP., its output being of 24 m.3/h.

A known drum mixer requires per batch 2 minutes' at a mixing time of seconds. Consequently, for an output of 24 m-/h. the drum mixer must have a capacity of 800 litres.

If one accepts as correct the statement of the specifica,- tions of the known drum mixers indicating a time of elaboration of 90 seconds per batch, the drum mixer must still have a capacity of 600 litres. Such a drum mixer has a weight of at least 3500 kg., requires an engine of at least 15 H.P. and its price is correspondingly and disadvantageously high. A charging device, in the present case, the rails 24 and car 25 and, in the case of the known mixer, a scraper and proportioning means, has to be furnished and extra-paid in both of the cases.

What We claim as new and desire to secure by Letters Patent is:

1. A mixer, particularly a concrete mixer with tub lift and tub-charging means, wherein a rotary mixing device is mounted on a rotary shaft extending longitudinally through the tub of said lift to provide a liftable mixing trough and wherein inclined guide rails of the tub lift form part of a machine frame of the mixer, comprising a pair of shafts rotatively mounted at the top of said machine frame, `a reversible electric motor carried by said frame and operatively connected with a first shaft of said pair of shafts, a first toothed wheel fixedly mounted on said first shaft, a second toothed wheel of a diameter different from that of said first toothed wheel on the second shaft of said pair of shafts and meshing with said first toothed wheel, at least one first rope drum fxedly mounted o-n said first shaft, at least one second rope drum fixedly mounted on said second shaft, said second rope drum and second shaft being rotated by said second toothed wheel in one direction and being freely rotatable relative Vto said second toothed wheel in the opposite direction, and at least one rope having one end fastened on said first rope drum `and its other end on said second rope drum and laid in several windings around a helically grooved pulley provided on said rotary shaft of the said mixing device.

2. A mixer, particularly a concrete mixer with tub lift and tub-charging means, wherein a rotary mixing device is mounted on a rotary shaft extending longitudinally through the tub of said lift to provide `a liftable mixing trough and wherein inclined guide rails of the tub lift form part of a machine frame of the mixer, comprising a pair of shafts rotatively mounted at the top of said machine frame, a reversible electric motor carried by said frame and operatively connected with a first `shaft of said pair -of shafts, a first toothed wheel xedly mounted on said first shaft, a second toothed wheel of a diameter different from ythat of said iirst toothed wheel on the second shaft o-f said pair of shafts and meshing with said first toothed wheel, a first pair of rope drums iixedly mounted one on each end of said first shaft, `a second pair of rope drums fixedly mounted on each end of said second shaft, `said second pair of rope drums and said second shaft being rotated by said second toothed wheel in one direction and being freely rotatable relative to said second toothed wheel in the opposite direction, and a pair of ropes having one end fastened on the respective drums of said first shaft and the other end on the respective drums of said second shaft and each rope being laid in several windings around a helically grooVed pulley provided on said rotary shaft of the said mixing device. 3. A mixer, particularly a concrete mixer with tub lift and tub-charging means, wherein a rotary mixing device is mounted on a rotary shaft extending longitudinally through the tub of said lift to provide a liftable mixing trough and wherein inclined guide rails of the tub lift form part of a machine frame of the mixer, comprising a pair of shafts rotatively mounted at the top of said machine frame, a reversible electric motor capable of operating at different speed in one and the opposite direction and carried by said frame and operatively connected with a first shaft of said pair of shafts, a first toothed wheel fxedly mounted on said first shaft, a second toothed wheel of a diameter different from that of said first toothed wheel on the second shaft of said pair of shafts and meshing with said rst toothed wheel, at least one first rope drum fixedly mounted on said first shaft, at least one second rop drum xedly mounted on said second shaft, said second rope drum and second shaft being rotated by said second toothed wheel in one direction and being `freely rotatable relative to said second toothed wheel in the opposite direction, and at least one rope having one end fastened on said first rope drum and its other end on said second rope drum and laid in several windings around a helically grooved pulley provided on said rotary shaft of the said mixing device.

i 4. A mixer, particularly a concrete mixer with tub lift and tub-charging means, wherein a rotary mixing device is mounted on a rotary shaft extending longitudinally through the tub of said lift to provide a liftable mixing trough and wherein inclined guide rails of the tub lift form part of a machine frame of the mixer, comprising a pair of shafts rotatively mounted at the top of said machine frame, a reversibile electric motor capable of operating at different speed in one and the opposite direction and carried by said frame and operatively connected with a first .shaft of said pair of shafts, a first toothed wheel fixedly mounted on said first shaft, a second toothed wheel of a diameter ldifferent from that of said first toothed wheel on the second shaft of said pair of shafts and meshing with said first toothed Wheel, at least one first rope drum fixedly mounted on said first shaft, at least one second rope drum fxedly mounted on said second shaft, said second rope drum and second shaft being rotated by said second toothed wheel in one direction and being freely rotatable relative to said Isecond toothed wheel in the opposite direction, and at least one rope having one end fastened on said first rope drum and its other end on said second rope drum and laid in several windings around a helically grooved pulley provided on said rotary Shaf-t of the said mixing device, the said mixing trough having a substantially semi-cylindrical cross section and comprising a discharge slide formed by extensions of a side wall and of the end walls of said trough, a grating being provided in the charging opening of said trough extending from the free side edges of said end wall extensions to the opposite side Wall edge of the trough.

5. A mixer as set forth in claim 4, wherein the said mach-ine frame is provided with a funnel-shaped slide arranged at certain height for receiving the concrete from the said mixing trough in its upper discharging position.

6. A mixer, particularly a concrete mixer with tub lift and tub-charging means, wherein a rotary mixing device is mounted on a rotary shaft extending longitudinally through the hub of said lift to provide a liftable mixing trough and wherein inclined guide rails of the tub lift form part of a machine frame of the mixer, comprising a pair of shafts rotatively mounted at the top of said machine frame, a reversible electric motor capable of operating at different speed in one and the opposite direction and carried by said frame and operatively connected with a first shaft of said pair of shafts, a first toothed wheel fixedly mounted on said first shaft, a second toothed Wheel of a diameter different from that of said first toothed wheel on the second shaft of said pair of shafts and meshing with said first toothed wheel, at least one first rope drum fxedly mounted on said first shaft, at least one second rope drum xedly mounted on said second shaft, said second rope drum and second shaft being rotated by said second toothed wheel in one direction and being freely rotatable relative to said second toothed wheel in the opposite direction, and at least one rope having one end fastened on said first rope drum and its other end on said second rope drum and laid in several windings around a helically grooved pulley provided on said rotary shaft of the said mixing device, and a trough-charging device comprising a pair of rails arranged in an inclined position with their upper ends situated laterally above Said mixing trough in its lower charging positions, and a tiltable transport car on said rails having a trap-door at its front end, carrier wheels arranged substantially below its centre of gravity, supporting rollers near its rear end and adjustable partition walls for proportioning by volume the materials to be mixed.

References Cited in the file of this patent UNITED STATES PATENTS 1,533,950 Schlich Apr. 14, 1925 FOREIGN PATENTS 440,217 Germany Feb. 1, 1927 1,092,437 France Oct. 23, 1933 

1. A MIXER, PARTICULARLY A CONCRETE MIXER WITH TUB LIFT AND TUB-CHARGING MEANS, WHEREIN A ROTARY MIXING DEVICE IS MOUNTED ON A ROTARY SHAFT EXTENDING LONGITUDINALLY THROUGH THE TUB OF SAID LIFT TO PROVIDE A LIFTABLE MIXING TROUGH AND WHEREIN INCLINED GUIDE RAILS OF THE TUB LIFT FORM PART OF A MACHINE FRAME OF THE MIXER, COMPRISING A PAIR OF SHAFTS ROTATIVELY MOUNTED AT THE TOP OF SAID MACHINE FRAME, A REVERSIBLE ELECTRIC MOTOR CARRIED BY SAID FRAME AND OPERATIVELY CONNECTED WITH A FIRST SHAFT OF SAID PAIR OF SHAFTS, A FIRST TOOTHED WHEEL FIXEDLY MOUNTED ON SAID FIRST SHAFT, A SECOND TOOTHED WHEEL OF A DIAMETER DIFFERENT FROM THAT OF SAID FIRST TOOTHED WHEEL ON THE SECOND SHAFT OF SAID PAIR OF SHAFTS AND MESHING WITH SAID FIRST TOOTHED WHEEL, AT LEAST ONE FIRST ROPE DRUM 